Soot is the main component of particulate matter (PM) generated in a combustion chamber of an internal combustion engine (particularly, a diesel engine). In order to accurately control the discharge amount of such soot to thereby reduce the same, the discharge amount of soot must be accurately estimated.
For example, a soot discharge estimating device for an internal combustion engine disclosed in Japanese Patent Application Laid-Open (kokai) No. 2007-46477 employs a method for accurately estimating the discharge amount of soot, even when the internal combustion engine is in a transient operation state, through use of a complex reaction model based on the mechanism of generation of soot.